Health data from a cohort of 33,346 middle-aged men and women was collected over a 16-year period to identify the major risk factors for osteoporotic fracture in this age group.

Diabetes was the main risk factor, being associated with a 2.4 times increased risk of fragility fracture. Other risk factors included mental illness and excessive alcohol consumption.

Lead researcher Dr Anna Holmberg, of Malmo University Hospital in Sweden, said: 'The link with diabetes was much stronger than we anticipated.'

The study was presented at the International Osteoporosis Foundation World Congress on Osteoporosis held in Canada last week. Other research presented at the conference found that weight loss could increase fracture risk, but so could obesity.

In the first study, Dr Bryan Whelan from Cork University Hospital in Ireland, looked at the relationship between weight and BMD at the hip, spine and thigh bone in 22,000 people aged over 50.

It found that post-menopausal women under 72kg and men under 81kg had an increased risk of osteoporosis.

Dr Whelan suggested that patients should be wary of dieting so that their weight fell below these limits.

But research presented by Dr Hong-Wen Deng of the University of Missouri in Kansas City showed that obesity could also accelerate bone loss.

The study of 1,988 Chinese and 4,489 white patients found that high muscle mass was associated with higher BMD, but increased fat mass was associated with lower BMD.